I guess the Decent skin contains customised speedcam icons. The speedcam image "strips" in the skin will override the 2 image strips in the UX.
If your not bothered about losing the customised speedcam icons you could just replace the 2 image files in the decent skin 800_480 folder with the 2 image files in the UX. ( make a backup copy of your skin first!)
Alternatively, if you upload your skin I will modify it so you can have both the "decent skin" customised icons & my traffic light icon